Ovarian failure is the most common cause of primary amenorrhea. In the presence of normal karyotype, ovarian failure is usually due to resistant ovary syndrome (ROS). These women typically present with primary amenorrhea, high serum level of follicle stimulating hormone (FSH), and follicles in the ovary as judged by transvaginal ultrasound or ovarian histology. There is no treatment for this condition at this time, only symptom management. If pregnancy is desired, the only option available is in vitro fertilization with donor eggs. These processes, besides being ethically unacceptable to many couples, are expensive, have a modest success rate, and expose both the donor and recipient to considerable medical risks. The infant resulting from the egg donation will not be genetically related to the legal mother. Recent findings that mutation in the FSH receptor (FSHR) gene causes ROS indicate that gene therapy could be an effective option in these patients who are interested in fertility. The goal of this project is to evaluate the utility of FSHR gene therapy in an animal model for ROS. In this proposal, we will (Specific Aim 1) construct an adenoviral vector expressing a normal copy of the FSHR (Ad-FSHR) under a universal (CMV) or granulose cell-specific (inhibin) promoter. In Specific Aim 2, we will test the ability of Ad-FSHR to infect and express FSHR in both COS and granulosa cells as well as to transcomplement the inactivating Finnish C566T mutation in a COS cell model. In Specific Aim 3, the therapeutic efficacy of a wild-type FSHR will be tested in vivo. The anovulatory infertile FSHRknock out (FORKO) mice will be treated by direct intraovarian injection of Ad-FSHR or control virus. Gross and histological analysis of uterus, long bones, and adipose tissues will be performed, and the ovaries will be weighed and examined for follicular development and the number of mature follicles, as well as FSH binding. We will assess cyclicity by vaginal smears and assay blood samples for estrogen, progesterone, testosterone, FSH, and LH levels to examine correction of hormonal imbalances. When ovarian function resumes, treated animals will be mated with normal size-matched male mice to assess the ability of treated FORKO mice to achieve pregnancy. This research will increase our understanding of the role of FSHR in ovarian homeostasis in an in vivo setting as well as spearhead the development of gene delivery as a novel therapeutic modality for treating infertility due to gonadal failure. Gene therapy is a rapidly developing field and may be a useful tool in treating several conditions in the area of women health that currently have no effective treatment available.